Vehicle sensitive retractor

ABSTRACT

A vehicle sensitive safety belt retractor is provided with actuating means responsive to acceleration of the vehicle for moving pawl means into engagement with ratchet means mounted on a belt strap reel of the retractor, and thereby preventing protraction of the belt. The actuating means includes mounting means provided with an arm, pendulum means having a cap in contact with the pawl means and freely suspended from the top of the arm and stop means associated with the arm for preventing horizontal displacement of the cap. Sliding friction, as well as entrapment of dirt particles and corroded material between the pendulum means and the top of the arm, is substantially avoided. The retractor is highly reliable in operation and inexpensive to maintain.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to seat belt retractors for passengers invehicles such as automobiles, and more particularly to an inertiaresponsive safety belt retractor which is vehicle sensitive, that is tosay, one responsive to acceleration of the vehicle, for preventingprotraction of the belt upon a predetermined acceleration of thevehicle. It is intended that the term "acceleration" as used hereinincludes the effects produced by cornering and braking.

2. Description of the Prior Art

Vehicle sensitive safety belt retractors have been recently developedwhich should significantly decrease the number of fatalities and seriousinjuries resulting from motor vehicle accidents. Most of theseretractors include a belt reel which is continually biased in aretracting direction, a pawl which is engageable with ratchet teeth onthe end of the belt reel, and an actuating mechanism having a pendulumin contact with the pawl and freely suspended from a ball and sockettype mount. When the pendulum is displaced from its normally verticalposition by an acceleration of the vehicle, it moves the pawl intoengagement with the ratchet teeth, preventing further protraction of thebelt. It is obviously of prime importance that the force necessary fordisplacement of the pendulum from the vertical position be correctlyestablished and maintained at the magnitude necessary for properactuation of the pawl. This requirement has, however, been difficult tomeet. Particles of dirt and corroded material entrapped between the balland the socket, as well as the sliding friction generated therebetween,can alter the acceleration required to displace the pendulum by amagnitude as high as one hundred percent or more. Unless regularlyserviced, the actuating mechanism of the retractor may becomeinsufficiently reliable in operation when subjected to changing climaticconditions for prolonged periods of time. Suspending the pendulum fromthe top of an upwardly extending projection reduces sliding friction andentrapment of dirt particles but requires additional parts machined toclose tolerances, thereby increasing manufacturing costs of theretractor. For the above reasons, retractors of the type describedgenerally result in lower reliability factors and higher production andmaintenance costs than are considered to be commercially acceptable.

SUMMARY OF THE INVENTION

The present invention provides an inertia responsive and vehiclesensitive seat belt retractor having an actuating means which is highlyreliable in operation and inexpensive to manufacture and maintain. Theretractor in which the actuating means is incorporated comprises asupport means, reel means rotatably mounted on the support means, beltmeans attached to the reel means for protraction and retraction withrespect thereto, biasing means for urging the reel means in a retractingdirection, ratchet means mounted on the reel means for rotationtherewith and pawl means mounted on the support means for engaging theratchet means to stop rotation of the reel means, thereby preventingfurther protraction of the belt means. The actuating means incorporatedin the retractor is responsive to acceleration of the vehicle andincludes: (1) mounting means comprising an arm having its topsubstantially parallel to the floor of the vehicle and having anaperture therein, (2) pendulum means freely suspended from the mountingmeans and comprising a pendulum weight on the lower end of a shaftconnected at its upper end to a cap having its upper surface contactingthe pawl means and its lower surface supported by the top of the arm and(3) stop means associated with the arm for preventing horizontaldisplacement of the cap.

During normal operation of the vehicle, the pendulum means remains in asubstantially vertical position. The pawl means does not engage theratchet means and the belt means can be protracted and retracted to suitthe convenience of the occupant. Acceleration of the vehicle which isgreater than a preselected magnitude causes the pendulum means to bedisplaced from its substantially vertical position. This displacementoperates to move the pawl means into engagement with the ratchet means,thereby preventing further protraction of the belt means.

The apparatus of this invention has advantageous structural features. Aunique pivoting movement provided by the cap and the top of the armsubstantially eliminates sliding friction, as well as the entrapment ofdirt particles and corroded material therebetween. Thus, theacceleration required for proper actuation of the pawl means can besustained at the preselected magnitude without periodic maintenance fora prolonged period of time. Moreover, the pivotal movement between thecap and the top of the arm provides a detent action which preventsmovement of the pendulum means due to accelerations of the vehicle belowthe preselected magnitude, such as those generated by road noise and thelike. The pendulum means remains in the substantially vertical positionand is not set in motion until its actuating movement is required.Hence, the mounting means is less subject to wear and the distance movedby the pendulum means during actuation of the pawl means remainsconstant. Further, these advantages are achieved without the need forproviding the arm with costly additional components such as an upwardlyextending projection or the like, that must be constructed andmaintained within close tolerences.

BRIEF DESCRIPTION OF THE DRAWING

The invention will be more fully understood and further advantages willbecome apparent when reference is made to the following detaileddescription of the preferred embodiments of the invention and theaccompanying drawings in which:

FIG. 1 is a longitudinal section, partially cutaway, of one form of avehicle safety belt retractor including the pawl, pendulum, cap, arm andstop means of the present invention.

FIG. 2 is a plan view, partially broken away, of the cap, arm and stopmeans of FIG. 1;

FIG. 3 is a longitudinal section, partially cutaway, of another form ofthe vehicle safety belt retractor of this invention;

FIG. 4 is a plan view, partially broken away of the cap, arm and stopmeans of FIG. 3; and

FIGS. 5 and 6 are longitudinal sections, partially cutaway, of stillother forms of the present vehicle safety belt retractor.

DETAILED DESCRIPTION OF THE DRAWING

Referring to FIGS. 1 and 2 the drawings, there is illustrated one formof a vehicle sensitive safety belt retractor incorporating the actuatingmeans of the present invention. Other forms of the retractor can also beused. The retractor, shown generally at 1 in the drawing, shouldtherefore be interpreted as illustrative and not in a limiting sense. Asillustrated, the retractor shown generally at 1, has a reel means 10rotatably mounted on a support means 12. The support means 12 is a loadbearing member and is provided with a mounting means 14 in the form of arigid extension adapted to be bolted or otherwise secured to ananchorage point on the vehicle (not shown). A belt means 16, formed of aflexible nylon web or the like, is attached to the reel means 10 forprotraction and retraction with respect thereto. The reel means 10 isprovided with a biasing means, such as a torsion return spring 11 or thelike, for biasing in a conventional manner the reel means 10 in aretraction direction. Fixedly mounted on the reel means 10 for rotationtherewith is a ratchet means 18, the periphery of which has a pluralityof circumferentially spaced ratchet teeth 20 formed by closely spacednotches or slots. As shown in the drawing, the ratchet means 18 may bedirectly mounted on the reel means 10. However, the definition of"ratchet means" in this specification is intended to include structure,including ratchet teeth, connected to but not directly mounted on thereel means. A pawl means 22 is mounted on pivot 23 journaled on thesupport means 12 for engaging the ratchet means 18 to stop rotation ofthe reel means 10, thereby preventing further protraction of the beltmeans 16. The pawl means 22 is moved into engagement with the ratchetmeans 18 by an actuating means, shown generally at 24, which isresponsive to acceleration of the vehicle. Each of the reel means 10,support means 12, mounting means 14, ratchet means 18 and pawl means 22is generally constructed of a suitable metal, such as heat treated steelor the like.

The actuating means 24 has a mounting means comprising an arm 26 whichmay be welded or otherwise attached at each end to the support means 12for increased rigidity, but which, of course, need not have both of itsends joined to a supporting member. Arm 26 is provided with an aperture28 and has its top 30 substantially parallel to the floor of the vehicle(not shown). The arm 26 can consist of a unitary member or be composedof two separate elements formed, for examples, of mild steel. Actuatingmeans 26 further includes a pendulum means comprising a pendulum weight34 on the lower end of a shaft 36 connected at its upper end to a cap38. The shaft 36 extends through the aperture 28 in a substantiallyvertical direction so that the upper surface 40 of cap 38 contacts pawlmeans 22 and the lower surface 42 of cap 38 is supported by the top 30of the arm 26. Each of the components of the pendulum means can be madeof a suitable plastic material, such as nylon orpolytetrafluoroethylene. Alternatively, the pendulum weight 34 can bemade of lead or other metal which is relatively heavy and dense, and theshaft 36 and cap 38 can be made of plastic material of the typedescribed or a suitable metal such as heat treated steel, brass or thelike. The various components of the pendulum means can be separatelyformed and then assembled, or integrally formed into a unitary structureby a molding operation.

The stop means can comprise a plurality of posts 31 positioned about theouter edge 33 of cap 38, for preventing horizontal displacement of thecap. As shown in FIGS. 3 and 4 the posts 31 need not be substantiallyperpendicular to the top 30 of arm 26, but may be disposed at an anglethereto. The angle, φ, between the posts and the top 30 of arm 26typically ranges from about 30° to 100° depending on the geometry of cap38. Posts 31 can be constructed of plastic material or the like, gluedto the surface of arm 26 or countersunk therein. As shown in FIG. 5, thestop means can comprise a ledge 37 extending downwardly into recessedposition 39 of arm 26, the top 30 of the recessed portion 39 forming thesupport for lower surface 42 of cap 38. To prevent displacement of thecap 38 from the recessed portion 39, the depth, d₁, of recessed portion39 should be greater than the distance, d₂, between the upper edge 41 ofpawl means 22 and the bottom 43 of ratchet means 18, as in the order ofabout 1.2 to 10 times greater. Similarly, as shown in FIGS. 1 and 3, theheight, h, of posts 31 should be in the order of about 1.2 to 10 timesgreater than the distance, d₂, between upper edge 48 of pawl means 22and bottom 43 of ratchet means 18.

During normal operation of the vehicle, the pendulum means remainsfreely suspended from the mounting means in a vertical position, withthe result that the lower surface 42 of cap 38 contacts and is supportedby top 30 of arm 26. The pawl means 22 rests on the upper surface 40 ofcap 38 and does not engage the ratchet means 18. As a result, the beltcan be protracted and retracted at any rate convenient to the occupantwithout inadvertently locking the retractor 1. Acceleration of thevehicle above a preselected magnitude, as in the order of about 0.3 gcauses the pendulum to be displaced from the substantially verticalposition. The cap 38 pivots on the mounting means until the top 30contacts edge portion 33 thereof. Simultaneously, the upper surface 40of cap 38 rises in a substantially vertical direction and moves the pawlmeans 22 into engagement with the ratchet teeth 20 of ratchet means 18,thereby preventing further protraction of the belt.

The acceleration required for displacement of the pendulum means fromits substantially vertical position depends upon the outside diameter,d, of the cap 38, the weight of the pawl means 22 and the distancebetween the center of mass of the pendulum weight 34 and a substantiallyhorizontal plane passing through the top 30. A representative example ofthe retractor 1 has a cap 38 having an outside diameter, d, of 0.3 inch,a pawl means 22 weighing 3 grams and a pendulum weight 34 having itscenter of mass located 0.5 inch from a substantially horizontal planepassing through the top 30 of arm 26. Thus constructed, the retractor 1is responsive to acceleration in the order of about 0.3 g in thesubstantially horizontal plane. Of course, the retractor 1 can bedifferently constructed so as to respond to acceleration having adifferent magnitude. Hence, the retractor 1 can have a cap 30 having anoutside diameter, d, of about 0.1 to 3 inches, a pawl means 22 weighingabout 0.5 to 300 grams and a pendulum weight 0.34 having its center ofmass located about 0.1 to 4 inches from a substantially horizontal planepassing through top 30 of arm 26.

As previously noted, when cap 38 is pivoted on the mounting means, itstop 30 of arm 26 contacts a relatively small portion (outer edge 33) ofcap 38. The "knife-edge" contact thereby created substantiallyeliminates sliding friction, as well as the entrapment of dirt particlesand corroded material between the cap 38 and the top 30. Such"knife-edge" contact can additionally be achieved prior to the pivotingoperation by providing cap 38 with a lower surface 42' (shown in FIG. 6)having a pointed or reduced or edge-like configuration. The arcuateconfiguration of surface 42' increases the sensitivity of the actuatingmeans and substantially eliminates entrapment of particulate materialbetween the cap and the arm. As a result, the acceleration required forproper actuation of the pawl means 22 can be sustained at a preselectedmagnitude in the order of at least about 0.3 g without periodicmaintenance.

An additional advantage resides in the detent action provided by thepivotal movement between the cap 38 and the top 30 of arm 26. Thependulum means does not commence to move until the center of mass of thependulum weight 34 is aligned with a substantially vertical planepassing through edge, 33 of cap 38. Accelerations below the preselectedmagnitude, such as those generated by road noise and the like, have amagnitude insufficient to bring the pendulum weight's center of massinto alignment with the substantially vertical plane through edge 38.The pendulum means remains in the substantially vertical position and isnot set in motion until its actuating movement is required. Hence, themounting means is less subject to wear and the distance moved by thependulum means during actuation of the pawl means 22 remains constant.Accordingly, the retractor has higher reliability and lower maintenancecosts than retractors inertially actuated by pendulum means suspendedfrom a ball and socket type mount.

The retractor which has been disclosed herein can, of course, bemodified in numerous ways without departing from the scope of theinvention. Arm 26 need not be parallel to the floor of the vehicle andcap 38 need not be normal to the arm 26. In each case, however, the top30 of arm 26 must be substantially parallel to the floor of the vehicle.The length, e, between surfaces 40 and 42 of cap 38 can range from about0.01 to 4 inches, preferably from about 0.10 to 0.5 inch, and itsconfiguration may be varied and include a configuration which isfrusto-comical or polygonal. Upper surface 40 of cap 38 can be cammedand pawl means 22 equipped with a downwardly extending ball-shapedprojection 46 to provide for uniform movement of the pawl means 22 upondisplacement of the pendulum means due to accelerations radiallyoperable thereon. A spring means such as a leaf spring 50 having one endriveted or otherwise secured to the support means 12 and the other endcontacting the top 48 of the pawl means 22 may optionally be employed tohold the pawl means 22 in contact with the cap 38, and, in oneembodiment, the spring means tension may be adjustable, as by adjustmentof the screw means 51, to change the preselected magnitude ofacceleration under which the pawl means activates. These and othermodifications are intended to fall within the scope of the presentinvention.

Having thus described the invention in rather full detail, it will beunderstood that these details need not be strictly adhered to but thatvarious changes and modifications may suggest themselves to one skilledin the art, all falling within the scope of the invention as defined bythe subjoined claims.

We claim:
 1. A safety belt retractor, comprising:a. support means; b.reel means rotatably mounted on said support means; c. belt meansattached to said reel means for protraction and retraction with respectthereto; d. biasing means for urging said reel means in a retractingdirection; e. ratchet means mounted in connection to said reel means forrotation therewith; f. pawl means mounted on said support means forengaging said ratchet means to stop rotation of said reel means andthereby prevent further protraction of said belt means; and g. actuatingmeans responsive to acceleration of said vehicle and including (1)mounting means comprising a substantially horizontal arm having anaperture therein, (2) pendulum means comprising a pendulum weight on thelower end of a shaft connected at its upper end to a cap having itsupper surface contacting said pawl means and its lower surface supportedon its outer edge by said arm and (3) stop means positioned on said armabout said outer edge for preventing horizontal displacement of saidcap, said pendulum means being freely suspended from said mounting meansand being displaceable by inertia from a normally substantially verticalposition, such displacement operating to move said pawl means intoengagement with said ratchet means.
 2. A retractor as recited in claim1, wherein said actuating means is responsive to acceleration having amagnitude in the order of at least about 0.1 g.
 3. A retractor asrecited in claim 1, wherein said pendulum means is not displaced from asubstantially vertical position by acceleration having a magnitude lessthan about 0.3 g.
 4. A retractor as recited in claim 1, wherein thelower surface of said cap has an outside diameter of about 0.1 to 3inches.
 5. A retractor as recited in claim 1, wherein said pawl meansweighs about 0.5 to 300 grams.
 6. A retractor as recited in claim 1,wherein said pendulum weight has a center of mass located about 0.1 to 4inches from a substantially horizontal plane passing through said lowersurface.
 7. A retractor as recited in claim 1, wherein said lowersurface has a pointed configuration.
 8. A retractor as recited in claim1, wherein said lower surface has a reduced configuration.
 9. Aretractor as recited in claim 1, including spring means for holding saidpawl means in contact with said upper surface of said cap.
 10. Aretractor as recited in claim 1, wherein said cap has a cammed surfaceand said pawl means has a downwardly extending ball-shaped projectionwhich contacts said cammed surface so as to provide for uniform movementof said pawl means upon displacement of said pendulum means byacceleration radially operable thereon.
 11. A retractor as recited inclaim 10 wherein said lower surface has a pointed configuration.
 12. Aretractor as recited in claim 10, wherein said surface has a reducedconfiguration.
 13. A retractor as recited in claim 1, including springmeans supported by said support means and connected to said pawl meansbiasing said pawl means in contact with said cap.
 14. A retractor asrecited in claim 13, including adjustable means for varying the springmeans tension.